1. Field of Invention
The present invention relates to a liquid crystal display that is capable of removing an after-image during a power-off operation, and a driving method therefor.
2. Description of Related Art
In general, a liquid crystal display includes a thin film transistor (TFT) substrate and a color filter substrate on which an electric field generating electrode is respectively formed and which face each other, and a liquid crystal layer interposed between the two substrates. The liquid crystal is moved by an electric field generated by applying voltage to the electrodes, thereby varying light transmittance to form an image.
The liquid crystal display includes a liquid crystal panel including a plurality of liquid crystal cells which are connected to gate lines and data lines, a data driver which applies a gray-scale display voltage to the data lines, a gate driver which applies a gate driving signal to the gate lines, a controller which controls the data driver and the gate driver, and a power supply which supplies a driving voltage.
The liquid crystal cell includes a liquid crystal capacitor for charging a gray-scale display voltage, and a TFT for applying the gray-scale display voltage to the liquid crystal capacitor in response to a gate-on voltage. The driving voltage which is supplied by the power supply includes a power voltage, a ground voltage, a gate-on voltage, a gate-off voltage, a common voltage and an analog power voltage.
When power supplied to the power supply is cut off, the power supply outputs an overall output voltage including the power voltage, the gate-on voltage, the gate-off voltage, the common voltage and the analog power voltage into 0V of a ground voltage level. When the gate-on voltage of the ground voltage level is applied to a gate of the TFT, the gray-scale display voltage applied to the liquid crystal capacitor is discharged as a leakage current through a channel of the TFT.
In the conventional liquid crystal display, when the power supply is cut off and the backlight unit is powered off, a pattern which is displayed on the liquid crystal panel does not disappear with the cut off of power but remains for a certain time as an after-image.